How can cellular phones or other RF signals interfere with microphone and hearing aid operation? Examines various telecommunications protocols (TDMA, CDMA, GSM, USDC, DECT) and various frequencies (900MHz, 1.8GHz, 2.4GHz) impact on microphone performance and discusses how EMI gets into the signal path. Presents solutions on reducing RFI and EMI by using Knowles "C" and "CX" microphone technology.

Knowles Electronics system nomenclature for laser-marking manufacturing date codes with week and year of manufacture and warranty period is detailed. Warranty extension markings are reviewed along with numerous examples of date code markings.